[A-OS11] Ocean Mixing Frontiers

[AOS11-P05] Performance of microstructure measurements using a deep float with a fast-response thermistor

*Shuo Zhai¹, Ichiro Yasuda¹ (1.Atmosphere and Ocean Research Institute, The University of Tokyo)

Keywords:turbulence, deep float

Turbulence measurements are required to quantify diapycnal flux of heat and substances which controls general ocean circulation, nutrients supply and marine ecosystem. Whereas, since turbulence measurements are still scarce especially in the deep ocean or near the bottom, autonomous microstructure observations are strongly desired. In the present study, as a step to realize autonomous microstructure observations using profiling deep floats, vibration impacts by active motors to adjust buoyancy on the fast-response thermistor (FP07) measurements were examined by using field data obtained in the western North Pacific in the vicinity of Japan. Although the FP07 measurements are much less sensitive to instrument vibration than velocity shear measurements, overestimations were evident when the float ascending speed was small and the motor vibration was active for acceleration, and those were proportional to and to the magnitude of the instrument acceleration. These are explained by the vibrational noise generated by high-frequency motion of the instrument, and the noise was amplified in the slow speed as a function of . By subtracting the vibrational noise estimated from the measured acceleration, corrected turbulence data in abyssal ocean or near ocean bottom can be obtained. The present study is the first study which discusses the impact of vibration on the turbulence estimation using FP07, and contributes to improving deep ocean turbulence measurements by proposing the effective methods which can be applied to Argo floats, gliders, CTDs and moorings.